Flow rate controlling apparatus

ABSTRACT

An apparatus for controlling a flow rate of fluid passing through a duct ( 10 ) includes a wedge ( 12 ) to produce a resistance against a flow of the fluid; pressure sensors ( 20 - 1, 20 - 2 ), to detect an inflow pressure and an outflow pressure at the upstream and the downstream of the duct ( 10 ), respectively, a flow rate controller ( 22 ) for measuring a flow rate corresponding to a differential pressure between the inflow and the outflow pressures, comparing the measured flow rate with a predetermined flow rate to regulate an opening angle at an outflow side of the duct ( 10 ) using a calculated opening angle, wherein the calculated opening angle being corresponded to a deviation of flow rate between the measured flow rate and the predetermined flow rate; and an error detector ( 28 ) for detecting an improper increase of the differential pressure to correctly adjust the opening angle regulated by the flow rate controller.

TECHNICAL FIELD

The present invention relates to a flow rate controlling apparatus tocontrol a flow rate of a fluid by regulating an opening angle dependingon a differential pressure, and more particularly, to a flow ratecontrolling apparatus and method thereof to prevent an abnormal supplyof a fluid by monitoring a flow rate of the fluid being subjected to aregulation in a real time.

BACKGROUND ART

In general, as known in the art, a duct is provided with a flow ratecontrolling apparatus to regulate in a real-time a flow rate of a fluidsupplied therethrough to a manufacturing apparatus according to amanufacturing recipe or the like.

FIG. 1 shows a schematic diagram of a conventional flow rate controllingapparatus.

As shown in FIG. 1, a duct 10 within which a fluid flows is providedwith a V-shaped wedge 12 formed in an inner wall thereof to cause adifferential pressure across the flow rate controlling apparatus. Thewedge acts as an element for producing a differential pressure betweenan upstream side (a left side of this drawing) from which the fluid isinflown and a downstream side (a right side of this drawing) to whichthe fluid is outflown by way of obstructing a sectional area of the duct10, wherein the differential pressure produced thereof is proportionalto the flow rate.

In addition, for example, the element for producing the differentialpressure includes an orifice, a porous filter, a nozzle, a capillarytube, and the like.

Further, a pair of pressure sensors 20-1 and 20-2 is located at theupstream and the downstream sides of the duct 10 while maintaining acertain distance from the wedge 12 to detect pressures induced by thewedge 12 at the upstream and the downstream sides of the duct 10,respectively. Alternatively, a single differential pressure sensor maybe employed instead of a couple of pressure sensors 20-1 and 20-2. Inthis regard, the single differential pressure sensor is provided on abranched duct communicated to the upstream and the downstream sides at acertain position of the duct 10, so that the sensor it directly measuresthe differential pressure between the pressures measured at both theupstream and the downstream sides of the duct 10.

Further, a flow rate controller 22 is electrically connected to thepressure sensors 20-1 and 20-2. The flow rate controller 22 receives aninflow pressure P1 and an outflow pressure transmitted from the pressuresensors 20-1 and 20-2, respectively, to produce a differential pressureΔP, and obtains a flow rate of a fluid currently passing through theduct 10 using the differential pressure ΔP.

Moreover, a valve 26 is provided at a location closer to the downstreamside of the duct 10 than the pressure sensor 20-2 of the outflow side,which is adapted to control the flow rate of a fluid supplied throughthe duct 10 by regulating a sectional area of a flow path (i.e., anopening angle). The valve 26 is coupled to a driving motor 24 whichprovides an operational force to the valve 26. Unlike the driving motor24, a solenoid, an actuator and the like may be used to control thevalve 26. These valve elements are subject to a control of the flow ratecontroller 22.

The operation of the flow rate controlling apparatus will be explainedwith reference to FIG. 2.

A fluid flows into the duct 10 from the upstream (the inflow) side tothe downstream (the outflow) side with a certain pressure. The fluidbecomes subject to a resistance to flow while passing through the wedge12, which results in a change of pressures between the inflow and theoutflow sides. More specifically, when the fluid passes the wedge 12which suddenly narrows in on a sectional area of the duct 10, thepressure applied on the fluid gets boosted to induce a differentialpressure between the inflow and the out flow sides.

Accordingly, pressures values P1 and P2 at the inflow and the outflowsides, respectively, are measured by the pressure sensors 20-1 and 20-2,respectively, and then the values are provided to the flow ratecontroller 22. Thereafter, from the flow rate controller 22, adifferential pressure value ΔP is produced using the inflow and theoutflow pressure values P1 and P2, the differential pressure value ΔP iscorresponding to a difference between the pressures P1 and P2. Further,a flow rate of a fluid currently passing through the duct 10 is measuredusing the differential pressure ΔP based on Formulas of the Bernoulli'stheorem and Conservation of mass.

Then, the flow rate controller 22 compares the measured flow rate with apredetermined reference flow rate to obtain a deviation of a flow ratecorresponding to the difference therebetween. Next, a opening angle isevaluated as to make the deviation of a flow rate zero (‘0’). A controlsignal corresponding to the calculated opening angle is then transmittedto the driving motor 24 to control the valve 26 to be open or closed.Accordingly, an opening ratio of a flow path at an end portion of theduct is changed, thereby substantially regulating the flow rate to atarget flow rate.

In addition to the above, joint parts in a shape of a flange may beformed at both of the end portions of the duct 10 to couple with theother ducts thereof.

However, the flow rate controlling apparatus as set forth above hasfollowing drawbacks.

Foreign particulars contained in the fluid could get adhered to withinthe wedge 12 causing a partial clogging in the wedge 12. Further, incase of the wedge 12 being deformed due to collisions with substances inthe fluid therewithin, a resistance to flow increases even further,resulting in an increase of a differential pressure ΔP of a fluid.Likewise, the flow rate controller 22 mistakenly considers that therehas been a substantial increase of the flow rate proportionally to theincreased differential pressure ΔP, thereby further closing the flowpath with the driving motor 24 and the valve 26 under control thereof.

As shown in FIG. 3, it is observed that an opening angle is remarkablylowered by the flow rate controller 22 compared with an opening angle ata normal operation.

As above, when a partial clogging occurs at the wedge 12, an amount ofthe fluid passing through thereof gets decreased. However, because theflow rate controlling apparatus erroneously considers this as anincrease of the flow rate in light of the differential pressure ΔP, theflow rate controller 12 controls the flow path to be further closed atthe rear end portion of the duct, which in turn, causes an insufficientsupply of the fluid in a manufacturing system.

For example, a CMP (Chemical-Mechanical Polisher), one of semiconductorequipments, uses slurry with polishing particulars therein as apolishing agent, the slurry being supplied through a fluid supplyingsystem thereto. However, the particulars in the slurry passing throughthe fluid supplying system inevitably causes a partial clogging, suchthat the slurry is not sufficiently supplied to the CMP, which resultsin an inferior manufacturing for many wafers manufactured. Therefore,critical loss cannot be avoided thereby.

Accordingly, there is a strong need to suggest a novel flow ratecontrolling apparatus to correctly control the opening angle regardlessof partial cloggings and the like.

DISCLOSURE OF INVENTION Technical Problem

An object of the present invention is, therefore, to provide a flow ratecontrolling apparatus capable of blocking an abnormal supply of a fluidin advance by way of monitoring in real-time an error occurred at thetime of controlling the opening angle.

Technical Solution

In accordance with an aspect of the present invention, there is providedan apparatus for controlling a flow rate of a fluid passing through aduct, which includes: means for producing a resistance against a flow ofthe fluid; means, located at an upstream and a downstream side of theduct, for detecting an inflow pressure P1 and an outflow pressure P2 atthe upstream and the downstream of the duct, respectively; a flow ratecontroller for measuring a flow rate corresponding to a differentialpressure ΔP between the inflow and the outflow pressures P1 and P2,comparing the measured flow rate with a predetermined flow rate toregulate an opening angle at an outflow side of the duct using acalculated opening angle, wherein the calculated opening angle beingcorresponded to a deviation of flow rate between the measured flow rateand the predetermined flow rate; and an error detector for detecting animproper increase of the differential pressure to correctly adjust theopening angle regulated by the flow rate controller.

In accordance with another aspect of the present invention, there isprovided a method of controlling a flow rate of a fluid passing througha duct, the method including the steps of: producing a differentialpressure between an inflow pressure and an outflow pressure in the ductdetected respectively by pressure sensors; measuring a flow ratecorresponding to the differential pressure to produce a measured flowrate; producing a fluctuation of a flow rate between the measured flowrate and a predetermined flow rate; calculating an opening anglecorresponding to the fluctuation of a flow rate to control a valve ofthe duct with a calculated opening angle; determining whether thedifference between the calculated opening angle and a normal openingangle is within a predetermined range, wherein the normal opening anglebeing corresponded to the predetermined flow; and adjusting the openingangle regulated by the flow rate controller if the difference betweenthe normal opening angle and the calculated opening angle is out of thepredetermined range.

Advantageous Effects

According to the present invention, it is possible to prevent an openingangle from being misadjusted in a flow rate controller due to a cloggingor the like in a wedge, and therefore, to prevent a badness of goods tobe manufactured in a manufacturing apparatus, thereby improving amanufacturing yield.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of preferred embodimentsgiven in conjunction with the accompanying drawings, in which:

FIG. 1 shows a schematic diagram of a conventional flow rate controllingapparatus;

FIG. 2 illustrates a block diagram of a conventional flow ratecontrolling apparatus shown in FIG. 1;

FIG. 3 describes a graph illustrating a problem of a partial clogging ata wedge side in a conventional flow rate controlling apparatus;

FIG. 4 depicts a schematic diagram of a flow rate controlling apparatusin accordance with the present invention; and

FIG. 5 illustrates a block diagram of a flow rate controlling apparatusshown in FIG. 4.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail with reference to the accompanying drawings, whereinlike numerical numbers refer to an identical member through thedrawings.

Referring to FIG. 4, there is shown a schematic view of a flow ratecontrolling apparatus in accordance with the present invention.

As shown in FIG. 4, the flow rate controlling apparatus includes a wedge12; a pair of pressure sensors 20-1 and 20-2 located at an upstream anda downstream side of a duct 10, respectively, apart from the wedge 12 todetect pressures at the upstream and the downstream sides of the duct10, respectively; a flow rate controller 22 to measure a deviation of aflow rate and to control of the operation of a driving motor 24 in amanner that the measured deviation of the flow rate becomes zero, tothereby regulate an opening angle of a flow path by allowing a valve 26to be open or closed under a control of the driving motor 24.

In the flow rate controlling apparatus, there may be a situation thatforeign particulars contained in the fluid gets clogged into the wedge12 causing a partial clogging and collides with the wedge 12 to deformthe wedge 12, to thereby closely block the flow path. In these cases, aresistance to flow is further increased, which entails an increase of adifferential pressure ΔP of a fluid. Therefore, the flow rate controller22 mistakenly determines that there has been a substantial increase ofthe fluid rate proportional to the increased differential pressure ΔP,so that it controls the valve 26 to be close. As a result, the fluiddoes not get provided smoothly to a manufacturing system which uses thefluid.

In order to overcome the above problem, the present invention furtherincludes a separate error detector 28 connected to the flow ratecontroller 28. The error detector 28 monitors continuously in real timeto detect whether the flow rate controller 22 performs an erroneouscontrol of an opening angle and to inform the situation to an operatoror the like with an alarm so that a serious problem can be preventedfrom occurring.

To this end, the error detector 28 acquires a predetermined flow rate(or a reference flow rate), which may be provided from a user or asystem of a manufacturing procedure, and an inflow pressure P1, ameasured flow rate and a calculated opening angle that are provided fromthe flow rate controller 22. Alternatively, the predetermined flow ratemay be directly acquired from the flow rate controller 22 as beingobtained by the flow rate controller 22.

The measured flow rate acquired from the flow rate controller 22 refersto a flow rate of a fluid derived from the differential pressure by theflow rate controller 22.

Further, the calculated opening angle acquired from the flow ratecontroller 22 indicates a control signal value to be used forcontrolling the operation of the driving motor 24 so as for the flowrate controller 22 to offset the deviation of the flow rate representingthe difference between the measured flow rate and the predetermined flowrate.

Accordingly, the error detector 28 produces a normal opening angle basedon a set of the predetermined flow rate, the inflow pressure P1 and themeasured flow rate using a certain equation. Then the error detector 28compares the normal opening angle with the calculated opening angle todetermine whether the difference therebetween is within a designatedrange. If it is determined that the difference is out of the range, itis regarded that the calculated opening angle is in error. In thisregard, the designated range may be differently settled depending on apressure. For example, if the pressure is in a stable condition, thedesignated range is settled in narrow, for example approximately 10%;and if the pressure is in an unstable or lower condition, the designatedrange will be increased inversely.

On the other hand, an alarm sound may be generated to inform of theerror, or an electrical alarm signal may be sent to associatedequipments in order to warn of the error.

The normal opening angle is calculated by the following Equation:

‘Normal opening angle’=K+S+B

where K represents a coefficient of opening angle pursuant to the rangeof a predetermined flow rate;

S is a fluctuation of a measured flow rate/a fluctuation of apredetermined flow rate; and

B is a compensation value to a fluctuation of the inflow pressure valueP1.

In this regard, the compensation value is used to reversely compensate avariation of an opening angle pursuant to a pressure fluctuation; andhas a separate value for each interval.

According to the above Equation, the coefficient of the opening angle Kof the predetermined flow rate is compensated with a fluctuation ratio Sof the flow rate and a compensation B of the pressure fluctuation.Therefore, it is possible to get a normal opening angle in real time.

Alternatively, it is possible to design that the error detector 28 has adatabase memory into which “a normal opening angle to a predeterminedflow rate” corresponding to “a normal status” as shown in a graph ofFIG. 3 is stored. In this case, the error detector 28 reads a normalopening angle to a predetermined flow rate from the database memory andcompares the normal opening angle with a calculated opening angleprovided from the flow rate controller 22. If the normal opening angleand the calculated opening angle are not accord with each other within apredetermined range, then an alarm is generated to warn of such error.

As described above, by providing to the exterior an alarm or an alarmsignal with the error detector, a subsequent operation by an operator orassociated devices may performed to block the fluid that is erroneouslyapplied to a manufacturing apparatus. Accordingly, it is possible toprevent an inferior of goods, e.g., wafers, manufactured by such amanufacturing apparatus employing a fluid.

While the invention has been shown and described with respect to thepreferred embodiments, it will be understood by those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. An apparatus for controlling a flow rate of a fluid passing through aduct, which comprises: means for producing a resistance against a flowof the fluid; means, located at an upstream and a downstream side of theduct, for detecting an inflow pressure P1 and an outflow pressure P2 atthe upstream and the downstream of the duct, respectively; a flow ratecontroller for measuring a flow rate corresponding to a differentialpressure ΔP between the inflow and the outflow pressures P1 and P2,comparing the measured flow rate with a predetermined flow rate toregulate an opening angle at an outflow side of the duct using acalculated opening angle, wherein the calculated opening angle beingcorresponded to a deviation of flow rate between the measured flow rateand the predetermined flow rate; and an error detector for detecting animproper increase of the differential pressure to correctly adjust theopening angle regulated by the flow rate controller.
 2. The apparatus ofclaim 1, wherein the error detector includes: means for producing anormal opening angle to the predetermined flow rate; means for comparingthe normal opening angle with the calculated opening angle; means fordetermining whether the difference between the normal opening angle andthe calculated opening angle is within a predetermined range; means forcompensating the opening angle regulated by the flow rate controller toadjust the opening angle if the difference between the normal openingangle and the calculated opening angle is out of the predeterminedrange.
 3. The apparatus of claim 1, wherein the error detector obtainsthe inflow pressure and the measured flow rate from the flow ratecontroller employed to produce the normal opening angle.
 4. Theapparatus of claim 1, wherein the normal opening angle is calculated asfollows:Normal opening angle=K+S+B, where K represents a coefficient of anopening angle pursuant to the range of a predetermined flow rate; S is afluctuation of a measured flow rate/a fluctuation of a predeterminedflow rate; and B is compensation to a fluctuation of the inflowpressure.
 5. A method of controlling a flow rate of a fluid passingthrough a duct, the method comprising the steps of: producing adifferential pressure between an inflow pressure and an outflow pressurein the duct detected respectively by pressure sensors; measuring a flowrate corresponding to the differential pressure to produce a measuredflow rate; producing a fluctuation of a flow rate between the measuredflow rate and a predetermined flow rate; calculating an opening anglecorresponding to the fluctuation of a flow rate to control a valve ofthe duct with a calculated opening angle; determining whether thedifference between the calculated opening angle and a normal openingangle is within a predetermined range, wherein the normal opening anglebeing corresponded to the predetermined flow; and adjusting the openingangle regulated by the flow rate controller if the difference betweenthe normal opening angle and the calculated opening angle is out of thepredetermined range.
 6. The method of claim 5, wherein the normalopening angle is represented as follows:Normal opening angle=K+S+B, where K represents a coefficient of anopening angle pursuant to the range of a predetermined flow rate; S is afluctuation of a measured flow rate/a fluctuation of a predeterminedflow rate; and B is compensation to a fluctuation of the inflowpressure.